Generously season the steaks on both sides with salt and pepper. Place the steaks directly on the embers about 2 inches apart. Grill until cooked to taste, 4 to 6 minutes per side for medium-rare
Build a charcoal fire and rake the coals into an even layer (leave the front third of the grill coal-free). When coals glow orange, fan them with a newspaper to blow off any loose ash.
Using tongs, lift the steaks out of the fire, shaking to dislodge any embers. Remove loose ash with a basting brush and arrange the steaks on a platter. Cover loosely with aluminum foil and let them rest while you prepare the sauce.
Make the hellfire hot sauce: Heat the olive oil in a cast-iron skillet. When the oil is hot, add the jalapenos, garlic, and cilantro. Cook the sauce over high heat until the jalapenos and garlic begin to brown, about 2 minutes. Immediately pour the sauce over the steaks and serve.